Easy way to convert Iterable to Collection

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忘了有多久
忘了有多久 2020-11-28 01:39

In my application I use 3rd party library (Spring Data for MongoDB to be exact).

Methods of this library return Iterable, while the rest of my

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  •  时光说笑
    2020-11-28 02:26

    Two remarks

    1. There is no need to convert Iterable to Collection to use foreach loop - Iterable may be used in such loop directly, there is no syntactical difference, so I hardly understand why the original question was asked at all.
    2. Suggested way to convert Iterable to Collection is unsafe (the same relates to CollectionUtils) - there is no guarantee that subsequent calls to the next() method return different object instances. Moreover, this concern is not pure theoretical. E.g. Iterable implementation used to pass values to a reduce method of Hadoop Reducer always returns the same value instance, just with different field values. So if you apply makeCollection from above (or CollectionUtils.addAll(Iterator)) you will end up with a collection with all identical elements.

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